ATI Radeon HD 4870 X2 - AMD Back On Top

Intro, Specifications and Related Info

AMD hasn't exactly kept the product we're going to be showing you here today a secret. Once NVIDIA launched the GeForce GTX 200 series, and AMD had a look at what the cards could do first hand, AMD's marketing machine was tuned up and revved to its redline expunging the features and benefits of their upcoming GPU. Then, when the initial products in the Radeon HD 4800 series launched, AMD's plan became quite clear.

The Radeon HD 4800 series didn't overwhelm NVIDIA's GTX 200 series with raw performance. In fact, the GeForce GTX 280 and 9800 GX2 were more powerful than the Radeon HD 4870. The Radeon HD 4800 series cards, however, were still excellent cards and they were offered at extremely competitive prices, which put significant pressure on NVIDA. At the time of their launch, the Radeon HD 4850 and Radeon HD 4870 were both less expensive and more powerful than the GeForce 9800 GTX and GeForce GTX 260, respectively.  Since then, NVIDIA has reacted with a quick round of price cuts.

While enthusiasts were contemplating the purchase of a new Radeon or GeForce, AMD then planted another seed and released some concrete details regarding the Radeon HD 4870 X2, as if to say, "Yeah, we've got you covered at the $300 price point and a new, ultra powerful behemoth is coming real soon too. Maybe you should hold onto your upgrade money for a bit?"

That behemoth is the Radeon HD 4870 X2. As its name suggests, the card features two RV770 GPUs running in tandem, for what is effectively a Radeon HD 4870 CrossFire configuration on a single PCB. Other than its pair of GPUs, however, the Radeon HD 4870 X2 has a few more differentiating factors we'll need to tell you about. Read on for the full scoop... 


ATI Radeon HD 4870 X2 Cards (Codename R700)

AMD ATI Radeon HD 4800 Series
Specifications and Features

  • 956 million transistors on 55nm fabrication process
  • PCI Express 2.0 x16 bus interface
  • 256-bit GDDR3/GDDR5 memory interface
  • Microsoft DirectX 10.1 support

    • Shader Model 4.1
    • 32-bit floating point texture filtering
    • Indexed cube map arrays
    • Independent blend modes per render target
    • Pixel coverage sample masking
    • Read/write multi-sample surfaces with shaders
    • Gather4 texture fetching
  • Unified Superscalar Shader Architecture

    • 800 stream processing units

      • Dynamic load balancing and resource allocation for vertex, geometry, and pixel shaders
      • Common instruction set and texture unit access supported for all types of shaders
      • Dedicated branch execution units and texture address processors
    • 128-bit floating point precision for all operations
    • Command processor for reduced CPU overhead
    • Shader instruction and constant caches
    • Up to 160 texture fetches per clock cycle
    • Up to 128 textures per pixel
    • Fully associative multi-level texture cache design
    • DXTC and 3Dc+ texture compression
    • High resolution texture support (up to 8192 x 8192)
    • Fully associative texture Z/stencil cache designs
    • Double-sided hierarchical Z/stencil buffer
    • Early Z test, Re-Z, Z Range optimization, and Fast Z Clear
    • Lossless Z & stencil compression (up to 128:1)
    • Lossless color compression (up to 8:1)
    • 8 render targets (MRTs) with anti-aliasing support
    • Physics processing support
  • Dynamic Geometry Acceleration

    • High performance vertex cache
    • Programmable tessellation unit
    • Accelerated geometry shader path for geometry amplification
    • Memory read/write cache for improved stream output performance
  • Anti-aliasing features

    • Multi-sample anti-aliasing (2, 4 or 8 samples per pixel)
    • Up to 24x Custom Filter Anti-Aliasing (CFAA) for improved quality
    • Adaptive super-sampling and multi-sampling
    • Gamma correct
    • Super AA (ATI CrossFireX configurations only)
    • All anti-aliasing features compatible with HDR rendering
  • Texture filtering features

    • 2x/4x/8x/16x high quality adaptive anisotropic filtering modes (up to 128 taps per pixel)
    • 128-bit floating point HDR texture filtering
    • sRGB filtering (gamma/degamma)
    • Percentage Closer Filtering (PCF)
    • Depth & stencil texture (DST) format support
    • Shared exponent HDR (RGBE 9:9:9:5) texture format support
  • OpenGL 2.0 support
  • ATI PowerPlay

    • Advanced power management technology for optimal performance and power savings
    • Performance-on-Demand

      • Constantly monitors GPU activity, dynamically adjusting clocks and voltage based on user scenario
      • Clock and memory speed throttling
      • Voltage switching
      • Dynamic clock gating
    • Central thermal management – on-chip sensor monitors GPU temperature and triggers thermal actions as required
  • ATI Avivo HD Video and Display Platform

    • 2nd generation Unified Video Decoder (UVD 2)

      • Enabling hardware decode acceleration of H.264, VC-1 and MPEG-2
      • Dual stream playback (or Picture-in-picture)
    • Hardware MPEG-1, and DivX video decode acceleration

      • Motion compensation and IDCT
    • ATI Avivo Video Post Processor

      • New enhanced DVD upconversion to HD new!
      • New automatic and dynamic contrast adjustment new!
      • Color space conversion
      • Chroma subsampling format conversion
      • Horizontal and vertical scaling
      • Gamma correction
      • Advanced vector adaptive per-pixel de-interlacing
      • De-blocking and noise reduction filtering
      • Detail enhancement
      • Inverse telecine (2:2 and 3:2 pull-down correction)
      • Bad edit correction
      • Full score in HQV (SD) and HQV (HD) video quality benchmarks
    • Two independent display controllers

      • Drive two displays simultaneously with independent resolutions, refresh rates, color controls and video overlays for each display
      • Full 30-bit display processing
      • Programmable piecewise linear gamma correction, color correction, and color space conversion
      • Spatial/temporal dithering provides 30-bit color quality on 24-bit and 18-bit displays
      • High quality pre- and post-scaling engines, with underscan support for all display outputs
      • Content-adaptive de-flicker filtering for interlaced displays
      • Fast, glitch-free mode switching
      • Hardware cursor
    • Two integrated DVI display outputs

      • Primary supports 18-, 24-, and 30-bit digital displays at all resolutions up to 1920x1200 (single-link DVI) or 2560x1600 (dual-link DVI)
      • Secondary supports 18-, 24-, and 30-bit digital displays at all resolutions up to 1920x1200 (single-link DVI only)3
      • Each includes a dual-link HDCP encoder with on-chip key storage for high resolution playback of protected content4
    • Two integrated 400MHz 30-bit RAMDACs

      • Each supports analog displays connected by VGA at all resolutions up to 2048x15363
    • DisplayPort output support

      • Supports 24- and 30-bit displays at all resolutions up to 2560x16003
    • HDMI output support

      • Supports all display resolutions up to 1920x10803
      • Integrated HD audio controller with up to 2 channel 48 kHz stereo or multi-channel (7.1) AC3 enabling a plug-and-play cable-less audio solution
    • Integrated AMD Xilleon HDTV encoder

      • Provides high quality analog TV output (component/S-video/composite)
      • Supports SDTV and HDTV resolutions
      • Underscan and overscan compensation
      • MPEG-2, MPEG-4, DivX, WMV9, VC-1, and H.264/AVC encoding and transcoding
      • Seamless integration of pixel shaders with video in real time
      • VGA mode support on all display outputs
    • ATI CrossFireX Multi-GPU Technology

      • Scale up rendering performance and image quality with two GPUs
      • Integrated compositing engine
      • High performance dual channel bridge interconnect


  • As the above list of specifications and features show, the new Radeon HD 4870 X2 has the exact same features as the Radeon HD 4870; it just has two GPUs.  Like the other members of the Radeon HD 4800 series, the Radeon HD 4870 X2 offers DX10.1 and Shader Model 4.1 support, the GPUs are manufactured on TSMC's 55nm process node, and both support ATI's CrossFireX multi-GPU technology.

    Because we've covered essentially all of the shared features of the Radeon HD 4800 and 3800 series cards before, we won't be going into them in depth again here.  However, we would recommend taking a look at a few recent articles to brush up on the tech if you're so inclined.

    Perusing the sampling of articles above will lay the groundwork for much of what we'll be showing you on the pages ahead.  But to reiterate some of what we explained in our initial coverage of the RV770, AMD is touting the GPU as the first solution to offer 1 TFLOPS of compute power, with higher clocked and multi-GPU offerings capable of even more.

    AMD acheived this feat by increasing the population of the architecture's SP count from 320 on the older RV670 to a 800 on the RV770. AA and Z/Stencil performance were enhanced as well, and the number of texture units was increased from 16 to 40. The 800 stream processing units are grouped in a new SIMD core layout, and the texture units, ROPs, and cache have been restructured to minimize transistor count, while also increasing performance. With the RV770, AMD claims that the SPs in the GPU offer 40% more performance per square millimeter that the previous generation, and that more aggressive clock gating offers improved performance per watt as well. Likewise, the newly streamlined design of the RV770 texture units reportedly offer 70% more performance per square mm with double the texture cache bandwidth and large increases in 32- and 64-bit filter rates.

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